Here are tools and links that made the difference for me and will hopefully assist other C# developers. This is a fraction of what is out there that might even be better, this is just the stuff that got me through. I also got help from more experienced developers with all of these concepts.
What it looks like.
The Code Behind C#
Here is the important part! Line 18 is the counter part to the C# Page Load method. And line 8 is the counter part to the C# txtMyTextBox_TextChanged Method!
It is very easy to to test exactly the portion of your code you wish to test by 'hijacking' methods and properties as you test, in order to 'mock' resources or code that you do not wish to test.
You can run the test from the browser console in Chrome tools.